In answer to your question, Myth, to my knowledge, calculates times
based on a persistent frame rate... add to that our digital age when
Programs might be at 30/60 fps HDTV, and the commercials in
24.97/29.97 fps SD, with frame rates switching back and forth between
program and commercial... and you see where the problem comes in.
Myth makes the length calculation as # of frames/fps = # of seconds...
when the fps is variable, this changes. I see this commonly with
Digital versions of things like NBC HD here in the states.
Secondly, you are recording via DVB, so all the card is doing is
dumping the stream to a disk... One program might be 60 minutes at 8
Megabit/s bitrate, the next might be 9 Mbit/s, the next might be 19
M/bit. In short, recording sizes are going to be variable based on
the resolution, bitrate, and framerate of the program broadcast.
Robert